The proposal describes five lines of work on the contents, structure and functioning of belief systems, including: (1) Distinctiveness as a determinant of perceptual selectivity; (2) Phenomenal contents of the mind; (3) Structure of concepts and belief systems; (4) Attitude change research applied to social problems; and (5) Use of historical data in psychological research. There is a progression in the five lines of work in that they investigate belief systems at their successive stages of formation, organization, and socially significant manifestation. The first line of work focuses on how, with our limited information encoding capacity, we selectively notice and encode the distinctive aspects of our social and physical environment. the second line of research seeks to provide a description of a significant portion of the content of childhood thought by sampling and content-analyzing children's undirected thoughts on topics that preoccupy them (the self, the family, school, etc.). The third line of work investigates the organization of this phenomenal content of belief systems, using our probiological model and the analysis of sequences in words and thoughts, to discover structures and functioning rules. The fourth section proposes a thorough application of the basic research on belief systems and attitude changes to two social problem areas, energy conservation and cardiac risk reduction. The fifth line of work explores implications on a broader societal level, using a historical data archive of eminent people of all times and places for testing hypotheses about the nature and forms of social progress.